The castle Scharfenstein (Czech Šarfenštejn or Ostrý, not to confuse with the Ostrý castle near Lovosice) was built in the middle of the 13th century by the Markvartitzers on royal estates. The first documented mention dates back to 1268. The original Sorbian population was supplemented by colonists from Saxony (not to be confused with today's Saxony). During the disputes between the then owners from the von Warttenberg family and the Upper Lusatian League of Six Towns, the castle was burned down in 1445. It was abandoned soon after, because in 1515 it is already mentioned as deserted.
Of the medieval castle, only a few parts of the outer walls and the ruins of the prominent keep enthroned above the valley remain today. It is particularly impressive because of its location on a narrow basalt ridge, which is surrounded on three sides by the river Ploučnice. The view into the valley of the river makes a visit to the castle ruins particularly attractive.